Keep those mozzies (mosquitoes) away!

Mosquitoes are a fact of life in the summertime but have you ever wondered how they track us down so quickly?  We've all had the experience where we're enjoying a nice summertime picnic and as soon as dusk arrives the mosquitoes show up one by one and start attacking.  How do they find us so quickly?  Mosquitoes are attracted to carbon dioxide, which seems a little unfair.  We release carbon dioxide every time we breathe out and to be even more tricky mosquitoes are specifically attracted to intermittent pulses of carbon dioxide.  Mosquitoes can follow carbon dioxide odor upstream to it's source (us).  This is always particularly clear to me when I am camping and I wake up in the morning to see both the condensation on the tent surfaced caused by my breath and the mosquitoes longingly pressed up against the screen of the tent.

Picture by JJ Harrison found on Wikipedia.org

Mosquitoes and other animals (including us) perceive a smell when small molecules in the air bind to a receptor and activate an olfactory neuron which then passes the message on to the brain.  Mosquitoes and other bugs have these receptors on an antennule on their head.  Receptors bind molecules based on their shape and chemical composition.  Most receptors are not perfect if a molecule is similar in shape to the intended molecule or present in a high concentration then it too will bind to the receptor.  A recent paper published in Nature (474:87-91) looked for molecules that would bind to the mosquito carbon dioxide receptor thus confusing the mosquito and limiting its ability to find us.  The scientists recorded the activity of the carbon dioxide receptor neuron and found one compound which activated the receptor for an unusually long period of time.  Such strong long-term activation of the carbon dioxide receptor could disable the response olfactory receptor neuron to carbon dioxide and should limit the mosquitoes' ability to track the carbon dioxide odor.  This is in fact what the researchers found; mosquitoes were placed in a wind tunnel with carbon dioxide being released from an air cylinder.  Fewer of the mosquitoes that were treated with molecule that activated the carbon dioxide receptor were able to find the carbon dioxide source and those that did took longer.  We can't stop breathing so it's a relief by blocking the ability of mosquitoes to detect and track carbon dioxide we may be able to hide our distinctive long range scent.